U.S. Pat. No. 4,912,011 discloses a light-sensitive material comprising a support and a light-sensitive layer provided thereon which contains silver halide, a reducing agent, a color image forming substance and a polymerizable compound. The silver halide, the reducing agent, the polymerizable compound and the color image forming substance are contained in microcapsules (light-sensitive microcapsules) which are dispersed in the light-sensitive layer. The U.S. patent corresponds to European Patent Provisional Publication No. 0203613A and Japanese Patent Provisional Publications No. 61(1986) 275742 and No. 61(1986)-278849.
An image forming method using the light-sensitive material is also disclosed in U.S. Pat. No. 4,912,011. The method comprises the steps of imagewise exposing to light the light-sensitive material, and heating the light-sensitive material. A latent image of the silver halide is formed by the exposure. The polymerizable compound is polymerized by heating within the area where the latent image has been formed. The light-sensitive material is then pressed on an image-receiving material to transfer the unpolymerized polymerizable compound with a color image forming substance to the image-receiving material to form a color image on the image-receiving material.
Further, a method of polymerizing the polymerizable compound within the area where the latent image of the silver halide has not been formed is disclosed in Japanese Patent Provisional Publications No. 61(1986)-243449, No. 61(1986)-260241, No. 2(1990)-141756 and No. 2(1990)-141757. The contents of the former two publications are described in European Patent Provisional Publication No 0202490A.
With respect to the heat development process, it is preferred that the development time is as short as possible and the heating temperature is as low as possible. In this regard, various heat development accelerators have been proposed. For example, U.S. Pat. No. 4,956,260 discloses numerous accelerators. These known accelerators are organic compounds.
By the way, an image recording apparatus for the above-described image forming method has been proposed (cf., U.S. Pat. Nos. 4,737,822, No. 4,783,683, No. 4,797,710, No. 4,819,032 and No. 4,825,041). In order to construct a compact image recording apparatus, a short development time and a low heating temperature are required. Even if the above-mentioned accelerators are used, the known light-sensitive materials have not yet satisfyed the requirements.